Oil content measuring device and refrigeration system using the same

Abstract

An oil content measuring device measures the oil content of a refrigerant in a supercritical or a vapor phase state. A refrigeration system uses the oil content measuring device. The oil content measuring device has an electrostatic capacity measuring device for measuring an electrostatic capacity of the refrigerant containing a refrigerating machine oil, a density measuring device for measuring a density of at least one of the refrigerant and the refrigerating machine oil, a computing device for performing a computation on correlation characteristics between the electrostatic capacity and an oil content which indicates the ratio of the amount of the refrigerating machine oil to the amount of the refrigerant containing the refrigerating machine oil, using the density measured by the density measuring device. An oil content determining device determines an oil content at the measuring time from an electrostatic capacity using the correlation characteristics obtained by the computing device.

Description

This application is based upon Japanese Patent Application No. 2001-206891, filed on Jul. 6, 2001.1. Field of the InventionThe present invention relates to an oil content measuring device for measuring a refrigerating machine oil within a refrigerant used in a refrigerating machine of an air conditioner, and to a refrigeration system using the same.2. Description of the Related ArtA refrigerating machine oil (i.e., a lubricating oil) for lubricating a refrigerant compressor in a refrigerating machine is important for ensuring the long-lasting durability of a compressor. Therefore, it becomes very important to know the amount of refrigerating machine oil in the refrigerant. More substantially, how much of the refrigerating machine oil is contained in the refrigerant compressor itself.As a conventional technology for measuring the amount of a refrigerating machine oil, "Measurement of Solubility of Refrigerant in Refrigerating Machine Oil by Electrostatic Capacity" in Transactions of ...

AI Technical Summary

Benefits of technology

When the oil content measuring device is constructed as above, the electrostatic capacity (C) of the refrigerant can be calculated at the temperature and pressure used in the measurement by making use of the density ({character pullout}) of the refrigerant or the refrigerating machine oil even though the refrigerant in the refrigerating machine is in a supercritical state or in a vapor phase state. The electrostatic capacity of the refrigerant changes greatly depending on the changes in temperature and pressure, for example, as in the case of a supercritical refrigerating cycle, to determine the correlation characteristics between the electrostatic capacity (c) and the oil content (.chi.) of the refrigerant. Consequently, it becomes possible to easily obtain the oil content (.chi.) of the refrigerant without preparing an enormous amount of given data in advance.

According to a ninth aspect of the present invention, each of electrodes (207, 208) of the electrostatic capacity measuring means (200) is shaped like a needle and is arranged in the piping (21) through which the refrigerant flows. Therefore, any container for housing the electrostatic capacity measuring means (200) can be eliminated, resulting in saved space and a cost reduction. In addition, since each of the electrodes (207, 208) is shaped like a needle, the electrodes are highly flexible. Additionally, arrangement is possible on a portion where the piping (21) is bent, which results in an excellent mounting ability.

Problems solved by technology

However, in the above conventional method, a target of the measurement is refrigerant in a liquid phase state and it only considers the change in electrostatic capacity using temperature as a parameter to obtain an actual oil content.

For instance, if such a method is to be applied in a supercritical refrigerating cycle where a refrigerant in a refrigerating machine is substantially in a supercritical state, a vapor phase state, or a gas-liquid double phase state, it is difficult to simply obtain the oil content by the above conventional method.

In other words, in the above supercritical state or the vapor phase state, compared to the liquid phase state, the electrostatic capacity of the refrigerant dramatically changes not only because of the temperature but also because of the pressure, this results in the need for an enormous amount of data that represents the relation between the electrostatic capacity and the oil content, which need to be prepared in advance.

This data is difficult to compile and manage.

However, the conventional measurement cannot be performed on both the discharge side and the suction side of the compressor (11) where the refrigerant is in a vapor phase state, so that it is hard to perform a proper measurement in the compressor (11) to obtain the oil content (.chi.) of the refrigerant.

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